The purpose of this grant is to complete the development, correlation with present invasive and radioactive gas distribution and clinical application of a new non invasive computer based methodology for the evaluation of cardiorespiratory function derived from the quantification of respiratory pressure and flows and a technique of multiple inert gas washout (MGW) from the lungs. This permits the simultaneous measurement of ventilation (VE), ventilation dispersion (sigma VE), and effective ventilation (VE/VA), cardiac output, dead space (VD/VT), ventilation:perfusion (VA/Qc plus anat. QS/QT approximately or equal to VA/QT), and VA/Qc dispersion (sigma VA/Q), lung water (LH2O), static and dynamic compliance, and a paramedic description of the large (R1) and small (R2) airway resistance and compliance (C1 and C2) factors, as well as a dynamic description of the pulmonary flow-volume-pressure (F-V-P) relationships, oxygen consumption (O2C), carbon dioxide production (CO2P), and respiratory quotient R/Q. This is suitable for use in critically ill patients who are being maintained on ventilatory support therapy. To develop statistical models of the interrelationship between ventilatory and circulatory abnormalities in various types of ARDS syndromes which can be used to develop specific algorithms which can help the clinician to optimize simultaneously administered ventilatory (V therapy) and cardiovascular (Q therapy) directed to obtain the best possible physiologic results in a given ARDS patient. To conduct a prospective randomized clinical trial of optimized physiologically directed cardiovascular (Q) and ventilation (V) therapy as modulated by on-line analysis of the primary and computer MGW and F-V-P variables and the predictive aspects developed from the statistical models developed in the above study, compared to the best standard therapy as conducted by component ICU physicians using only the standard parameters of cardiovascular and blood gas measurements to define cardiac and ventilatory management. In addition the MGW and F-V-P techniques are being used to evaluate a new method of High Frequency Ventilation in both clinical and experimental settings.